When a pair of stereo-images formed by photographing the same views or objects as separated from each other by the eyepoint distance are observed simultaneously with both eyes, such views or objects will be able to be viewed three-dimensionally viewed stereo-images is called a stereo-viewer.
In a conventional stereo-viewer, two oculars are arranged as separated from each other by the eyepoint distance and an inserting hole is formed in the horizontal direction, i.e., the same direction as the direction of arranging the oculars in front of them. Stereo-images are arranged on a stereo-sheet provided in a roll film type, and the sheet is equally divided into two halves in the width direction. One of the stereo-images of the pair is arranged on the upper half side of the divided stereo-sheet, and the other stereo-image is arranged on the lower half side so as to continuously provide stereo-images in many sets in the lengthwise direction of the stereo-sheet. Such stereo-sheet is inserted into the inserting hole and is set in the horizontal direction of the stereo-viewer, and light is taken in through a translucent light taking plate. The light will pass through the stereo-images and will be led to the oculars so that the observer may view a three-dimensional picture image by the pair of stereo-images.
In such case, the two oculars are arranged on the same level and the stereo-images of the pair are divided into an upper half and lower half as mentioned above and are in different level positions. Therefore, in order to lead the light from the stereo-images to the oculars, it is necessary to change the direction of the light in a vertical direction. In such stereo-viewer formed having the stereo-sheet inserted in the horizontal direction, in order to solve this problem, a reflector has been set to change the direction of the path of the light to be in a vertical direction by reflecting the light with the reflector.
Therefore, it is necessary to fit such stereo-viewer with a reflector in addition to the two oculars. Thus, the component parts increased to complicate the structure.
There is another known stereo-viewer wherein the stereo-sheet is formed to be of a rotary type. Therein, the stereo-sheet is formed to be circular, many stereo-images are arranged near the periphery of the sheet, and the stereo-images of the set are arranged as separated from each other by 180 degrees. A semicircular inserting groove is formed in the stereo-viewer so that the stereo-sheet may be set in this groove. When the stereo-sheet is rotated while in sliding contact with the inserting groove, the stereo-images of the pair will be opposed to the two oculars so that three-dimensional picture images by respective paris of stereo-images may be viewed continuously.
In this stereo-viewer, as a pair of stereo-images are opposed directly to the oculars on the same level, no reflector to change the direction of the path of the light will be required. However, as the stereo-sheet is rotated in sliding contact with the inserting groove, the stereo-sheet is likely to be damaged on its peripheral edge and to be broken by the rotating operation within the semicircular inserting groove. Further, in order that three-dimensional picture images may be continuously viewed with respective stereo-images, the respective stereo-images must be arranged at regular intervals near the periphery of the stereo-sheet. It is so difficult and toilsome to arrange respective stereo-images at regular intervals that the stereo-sheet is difficult to fabricate.